Carcinogenesis studies will be continued to induce gastric cancer in mice by means of oral n-ethyl-n'-nitro-n-nitrosoquanidine. In some studies, x-irradiation to the stomach will be used to enhance the chemical carcinogenesis. Target cells will be derived to evaluate hepatic immune reactivity utilizing an assay for cytotoxicity using the murine C-1300 neuroblastma system. The lymphocyte-dependent antibody (LDA) or "Arming" assay will be used because of its sensitivity for examining the immune reactivity of liver reticulum cells in situ. Xenogenic sera from rabbits are highly active in the LDA assay in vitro; we will carry out experiments aimed at evaluating this phenomenon using the isolated perfused murine liver. We hope to obtain gastric tumors for explanation and the subsequent development of target lines. Liver perfusion studies will be performed and liver Kupfer cells will be examined for their capacity to be "armed" with xenogeneic sera. If successful, we hope to study parameters required to demonstrate killing of metastatic tumors in the liver.